This invention relates generally to sewing machines. In a more particular aspect, the present invention pertains to an attachment apparatus for synchronizing movements of a presser foot bar and a feed foot bar of a sewing machine with movement of a needle bar of the sewing machine.
Various sewing machine apparatus both for domestic use and commercial use have been developed. Conversion apparatus for converting a domestic sewing machine into one capable of feeding and stitching workpieces of extra thickness at cost substantially less than that required for the purchase of a commercial sewing machine have been developed as disclosed in my U.S. Pat Nos. 3,952,675; 4,296,703; 4,323,020 and 4,341,172. These conversion apparatus have feed mechanisms which grip both the top and bottom surfaces of the workpiece. These mechanisms have included the addition of a feed foot bar whose oscillation and reciprocation have had to be synchronized with other actions during a sewing cycle.
In my prior apparatus disclosed in the aforementioned patents, various means of operating the feed foot bar have been disclosed. Most of these have driven the feed foot bar with both feed and lift rods, but one embodiment shown in U.S. Pat. No. 3,952,675 (FIGS. 8 and 9) synchronizes the lifting of the feed foot bar and a presser bar with the rotation of a rotating cylinder or disk driving a needle bar. This requires a construction which accommodates the rotary motion of the rotating disk and the intervening motion of a link connecting the disk to the needle bar.
Despite the utility of my previous conversion apparatus, there is the need for an improved sewing machine, and attachment apparatus for a sewing machine, which more simply synchronizes the lifting and lowering of a feed foot bar and presser foot bar with the reciprocation of a needle bar.